feat(dist): crates.io + binstall + Windows install.ps1 + license files

Distribution prep on the road to public availability (plan steps 2–3a).

- Cargo.toml: publish-ready (drop publish=false; homepage/keywords/
  categories/exclude) + [package.metadata.binstall] with per-target
  overrides (linux-gnu->musl, windows-msvc->gnu/gnullvm). dry-run clean.
- scripts/install.ps1: Windows `irm | iex` one-liner — written but
  untested here (no PowerShell; validate on Windows). README Windows block.
- README.md (new); LICENSE-MIT + LICENSE-APACHE (dual, (c) Lazy
  Evaluation Ltd); CONTRIBUTING.md (inbound=outbound dual-license note).
- ADR-0055 Amendment 1 (install.ps1), ADR-0056 (crates.io/binstall),
  README index + plan updates.

The actual `cargo publish` remains a gated maintainer step (token,
irreversible) at a new tagged release; real cargo-binstall validation
pending.

docs/adr/0055-curl-sh-install-script.md

@@ -52,11 +52,22 @@ Ship **`scripts/install.sh`**, run as
   but adds a moving part; the **Gitea repo raw URL** is simplest and the
   binaries live there anyway (user decision). The website may later
   *reference* the same command.
-- **`install.ps1` (Windows):** deferred — Windows users go via Scoop /
-  winget (D3, §3). 
 - **Uploading `install.sh` as a release asset** for a stable link:
   optional; the branch raw URL is fine for now.
 
+## Amendment 1 — `install.ps1` (Windows) added (2026-06-17)
+
+Windows was originally deferred to Scoop/winget; the user opted for **both**
+a PowerShell one-liner now *and* package managers later. Added
+**`scripts/install.ps1`** (`irm <url> | iex`): maps the host CPU to our
+`*-windows-gnu`/`-gnullvm` `.exe`, resolves the latest release (or
+`-Version`/`RDBMS_VERSION`), downloads + **SHA-256-verifies**, installs to
+`%LOCALAPPDATA%\Programs\rdbms-playground` (`-InstallDir`/`RDBMS_INSTALL_DIR`
+override), and adds that dir to the **user PATH**. **Caveat:** unlike
+`install.sh` (verified end-to-end), this was **written but not tested from
+this environment** (no PowerShell available) — validate on a real Windows
+host. Scoop/winget (D3) remain the idiomatic package-manager routes.
+
 ## Consequences
 
 - A first-time user runs one line and gets a checksum-verified binary on